/*
You are climbing a stair case. It takes n steps to reach to the top.

Each time you can either climb 1 or 2 steps. In how many distinct ways can you climb to the top?
*/
public class Solution {
    public int climbStairs(int n) {
        // Start typing your Java solution below
        // DO NOT write main() function
        if (n == 0)
            return 0;
        if (n == 1)
            return 1;
        if (n == 2)
            return 2;
        int total = 0;
        int first = 1;
        int second = 2;
        for (int i=2; i< n; i++) {
            total = first + second;
            first = second;
            second = total;
        }
        return total;
    }
}
